Examples of typical known wireless power transmission systems include magnetic-field-coupling power transmission systems in which power is transmitted from the primary coil of a power transmitting apparatus to the secondary coil of a power receiving apparatus using a magnetic field. high accuracy is required in the relative positional relationship between the primary coil and the secondary coil when transmitting power using magnetic-field-coupling because electromotive force is strongly influenced by the magnitude of magnetic flux passing through each coil. In addition, use of coils makes it is difficult to reduce the sizes of the power transmitting and power receiving apparatuses.
On the other hand, electric-field-coupling wireless power transmission systems are known, as disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-531009 and Japanese Unexamined Patent Application Publication No. 2009-296857. In these systems, power is transmitted from the coupling electrode of a power transmitting apparatus to the coupling electrode of a power receiving apparatus through an electric field. This method allows the accuracy of the relative positional relationship between the coupling electrodes to be relatively low and allows the sizes and thicknesses of the coupling electrodes to be reduced.
FIG. 1 illustrates the basic configuration of the power transmission system disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2009-531009. This power transmission system includes a power transmitting apparatus and a power receiving apparatus. The power transmitting apparatus includes a high-frequency voltage generator circuit 1, a passive electrode 2, and an active electrode 3. The power receiving apparatus includes a high-frequency voltage load circuit 5, a passive electrode 7, and an active electrode 6. As a result of the active electrode 3 and the active electrode 6 being arranged to be close to each other with a gap 4 therebetween, these two electrodes are coupled to each other through an electric field.
The passive electrode of the power transmitting apparatus, the active electrode of the power transmitting apparatus, the active electrode of the power receiving apparatus, and the passive electrode of the power receiving apparatus have a common normal line passing through the centers thereof.
In the power transmission system disclosed in Japanese Unexamined Patent Application Publication No. 2009-296857, a power transmitting apparatus includes a first resonant circuit that resonates with an AC signal generated by an AC signal generator and a power feeding electrode. A power receiving apparatus includes a power receiving electrode that generates an electric signal, a second resonant circuit that resonates with the electric signal, a rectifier that generates a DC power from the electric signal with which the second resonant circuit is resonating, and a circuit load. The active electrode and passive electrode of the power transmitting apparatus are arranged in the same plane, and the active electrode and passive electrode of the power receiving apparatus are arranged so as to face the corresponding electrodes of the power transmitting apparatus with a predetermined separation therebetween.